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Influence of chemical reaction rate, diffusion and pore structure on the regeneration of a coked Al2O3-catalyst

Titelangaben

Tang, Dahai ; Kern, Christoph ; Jess, Andreas:
Influence of chemical reaction rate, diffusion and pore structure on the regeneration of a coked Al2O3-catalyst.
In: Applied Catalysis A: General. Bd. 272 (2004) Heft 1–2 . - S. 187-199.
ISSN 0926-860X
DOI: https://doi.org/10.1016/j.apcata.2004.05.040

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Link zum Volltext (externe URL): Volltext

Abstract

As a contribution to a better basic understanding and an accurate modelling of the regeneration of coked catalyst particles, the following investigations were done with pure Al2O3 as a model catalyst: (1) determination of the intrinsic and effective kinetics of coke burn-off; (2) characterisation of the catalyst’s morphology with respect to the influence of the carbon load on the surface area, porosity, pore diameter, and tortuosity; (3) measurement of radial coke profiles within partly regenerated particles; (4) numerical simulation of the regeneration within coked particles and comparison with experimental data of radial coke profiles and the time needed for a certain degree of burn-off. For the modelling of coke burn-off within single particles, the chemical reaction rate, pore diffusion, radial gradients of the O2- and the carbon-concentration, and the influence of the carbon load on the porosity and tortuosity have to be considered. Only the resistances of external heat and mass transfer and of intraparticle heat conduction can be neglected, at least for particle sizes and temperatures of technical relevance for fixed beds (<5 mm, <700 °C). The measured and numerically simulated data according to this model presented in detail are in good agreement. The results show that temperatures above about 400 °C are needed to achieve regeneration within an acceptable timeframe. On the other hand, a temperature of more than about 500 °C will not anymore accelerate the burn-off, at least in case of fixed bed reactors with particles in the region of mm. This effect can be attributed to the increasing strength of pore diffusion resistance, and eventually the complete resistance is confined to the outer carbon-free shell.

Weitere Angaben

Publikationsform: Artikel in einer Zeitschrift
Begutachteter Beitrag: Ja
Keywords: Pore structure; Regeneration; Coke burn-off; Tortuosity; Effective diffusion
Institutionen der Universität: Fakultäten > Fakultät für Ingenieurwissenschaften
Fakultäten > Fakultät für Ingenieurwissenschaften > Lehrstuhl Chemische Verfahrenstechnik
Fakultäten > Fakultät für Ingenieurwissenschaften > Lehrstuhl Chemische Verfahrenstechnik > Lehrstuhl Chemische Verfahrenstechnik - Univ.-Prof. Dr.-Ing. Andreas Jess
Fakultäten
Titel an der UBT entstanden: Ja
Themengebiete aus DDC: 500 Naturwissenschaften und Mathematik > 540 Chemie
600 Technik, Medizin, angewandte Wissenschaften > 600 Technik
600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften
600 Technik, Medizin, angewandte Wissenschaften > 660 Chemische Verfahrenstechnik
Eingestellt am: 24 Apr 2015 09:03
Letzte Änderung: 24 Apr 2015 09:03
URI: https://eref.uni-bayreuth.de/id/eprint/10681